ORIGINAL ARTICLE Impaired Limb Reaction to Displacement of Center of Gravity in Rats with Unilateral Striatal Ischemic Injury Cameron W. Nobile & Julie M. Palmateer & Jackie Kane & Patricia D. Hurn & Timothy Schallert & DeAnna L. Adkins Received: 24 January 2014 /Revised: 4 March 2014 /Accepted: 5 March 2014 /Published online: 2 April 2014 # Springer Science+Business Media New York 2014 Abstract Clinical stroke often results in impaired balance and increased vulnerability to severe injuries due to falling. To evaluate potential preclinical treatments that might target these deficits, it will be important to include tests capable of assessing these impairments chronically in animal models. Previously, we developed a postural instability test (PIT) that revealed chronic, unilateral impairments in postural stability in rat models of hemi-Parkinson’ s disease (PD) and of unilat- eral cervical spinal cord injury. Here, we investigated whether this test was also capable of revealing long-term stroke- induced impairments in postural support in rats. Additionally, we examined the ability of more common tests of sensorimo- tor function to detect chronic impairments. We found that the PIT detected chronic deficits in postural stability/balance en- during for up to 6 weeks post-stroke, outlasting impairments detected in other tests of forelimb sensorimotor function, including asymmetries in upright postural support (cylinder test) and vibrissae-evoked forelimb placing. Keywords Ischemia . Endothelin-1 . Balance . Striatum . Motor cortex . Stroke Introduction Many severe brain injuries and neurological diseases result in chronic postural instability. Stroke patients experience an especially high incidence of impaired balance maintenance, greatly increasing the risk for fall-related injuries [1–3]. A number of tests have been developed to assess the degree of postural instability in humans; however, few balance tests have been developed for use in rats [4, 5]. Further, evidence suggests that in both rats and humans, deficits in postural stability can be ameliorated by compensatory strategies such as shifting more weight onto the unimpaired limb [6–12]. This compensatory behavior can make it difficult to assess balance in rodents, and thus tests should be used that unmask the contribution of individual limbs, disentangling recovery of function in the impaired limb from adaptive compensation by the contralateral or less-impaired limb [8, 13, 14]. In 2008, Woodlee et al. [14] presented the postural insta- bility test (PIT), a refinement of a previously developed test [10, 15–17], which permitted the experimenter to probe the contribution of each forelimb in stabilizing the center of gravity after unilateral infusions of the dopamine-depleting neurotoxin 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB), a model of Parkinson’ s disease (PD). This task was shown to be highly sensitive to long- term impairments in the contralateral forelimb when used to regain balance. Recently, the PIT has also been used to mea- sure postural instability in rats with unilateral cervical spinal cord injuries [13]. However, this test has not been used to test postural deficits following experimental unilateral stroke. In the present study, unilateral focal infusion of endothelin- 1 (ET-1) into the striatum was used to induce severe stroke- like ischemic damage to the sensorimotor cortex and striatum. The rats were subsequently tested for 6 weeks. Postural sta- bility and forelimb use asymmetry during vertical exploration and vibrissae-induce forelimb placing were examined. C. W. Nobile : J. Kane : T. Schallert Department of Psychology, University of Texas at Austin, Austin, TX, USA J. M. Palmateer : P. D. Hurn Department of Neuroscience Section of Neurobiology, College of Natural Sciences, University of Texas at Austin, Austin, TX, USA D. L. Adkins (*) Department of Neurosciences, College of Medicine and Health Sciences and Research, College of Health Professions, Medical University of South Carolina Charleston, 173 Ashley Ave, CRI 404D, Charleston, SC 29425, USA e-mail: adkinsdl@musc.edu Transl. Stroke Res. (2014) 5:562–568 DOI 10.1007/s12975-014-0339-9